The Erie Canal is a historic canal in upstate New York that runs east-west between the Hudson River and Lake Erie. Completed in 1825, the canal was the first navigable waterway connecting the Atlantic Ocean to the Great Lakes, vastly reducing the costs of transporting people and goods across the Appalachians. In effect, the canal accelerated the settlement of the Great Lakes region, the westward expansion of the United States, and the economic ascendancy of New York State. It has been called "The Nation's First Superhighway."

A canal from the Hudson to the Great Lakes was first proposed in the 1780s, but a formal survey was not conducted until 1808. The New York State Legislature authorized construction in 1817. Political opponents of the canal, and of its lead supporter New York Governor DeWitt Clinton, denigrated the project as "Clinton's Folly" and "Clinton's Big Ditch". Nonetheless, the canal saw quick success upon opening on October 26, 1825, with toll revenue covering the state's construction debt within the first year of operation. The westward connection gave New York City a strong advantage over all other U.S. ports and brought major growth to canal cities such as Albany, Utica, Syracuse, Rochester, and Buffalo.

The construction of the Erie Canal was a landmark civil engineering achievement in the early history of the United States. When built, the 363-mile (584 km) canal was the second-longest in the world (after the Grand Canal in China). Initially 40 feet (12 m) wide and 4 feet (1.2 m) deep, the canal was expanded several times, most notably from 1905 to 1918 when the "Barge Canal" was built and over half the original route was abandoned. The modern Barge Canal measures 351 miles (565 km) long, 120 feet (37 m) wide, and 12 feet (3.7 m) deep. It has 34 locks, including the Waterford Flight, the steepest locks in the United States. When leaving the canal, boats must also traverse the Black Rock Lock to reach Lake Erie or the Troy Federal Lock to reach the tidal Hudson. The overall elevation difference is about 565 feet (172 m).

The Erie's peak year was 1855, when 33,000 commercial shipments took place. It continued to be competitive with railroads until about 1902, when tolls were abolished. Commercial traffic declined heavily in the latter half of the 20th century due to competition from trucking and the 1959 opening of the larger St. Lawrence Seaway. The canal's last regularly scheduled hauler, the Day Peckinpaugh, ended service in 1994.

Today, the Erie Canal is mainly used by recreational watercraft. It connects the three other canals in the New York State Canal System: the Champlain, Oswego, and Cayuga–Seneca. Some long-distance boaters take the Erie as part of the Great Loop. The canal has also become a tourist attraction in its own right—a number of parks and museums are dedicated to its history. The Erie Canalway Trail is a popular cycling path that follows the canal across the state. In 2000, Congress designated the Erie Canalway National Heritage Corridor to protect and promote the system.